Manufacturing method, surface-emitting laser device, surface-emitting laser array, optical scanner, and image forming apparatus

ABSTRACT

A manufacturing method for manufacturing a surface-emitting laser device includes the steps of forming a laminated body in which a lower reflecting mirror, a resonator structure including an active layer, and an upper reflecting layer having a selective oxidized layer are laminated on a substrate; etching the laminated body to form a mesa structure having the selective oxidized layer exposed at side surfaces thereof; selectively oxidizing the selective oxidized layer from the side surfaces of the mesa structure to form a constriction structure in which a current passing region is surrounded by an oxide; forming a separating groove at a position away from the mesa structure; passivating an outermost front surface of at least a part of the laminated body exposed when the separating groove is formed; and coating a passivated part with a dielectric body.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 13/127,531filed on May 4, 2011 as a Section 371 national stage of InternationalApplication No. PCT/JP2009/069596 filed on Nov. 12, 2009 which claimsthe priority of Japanese Patent Applications Nos. 2008-296195,2009-098657 and 2009-230090 filed with the Japanese Patent Office onNov. 20, 2008, Apr. 15, 2009 and Oct. 2, 2009, respectively.

TECHNICAL FIELD

The present invention relates to manufacturing methods, surface-emittinglaser devices, surface-emitting laser arrays, optical scanners, andimage forming apparatuses and, more specifically, to a manufacturingmethod for manufacturing a surface-emitting laser device, asurface-emitting laser device that emits laser light in a directionperpendicular to a substrate, a surface-emitting laser array, an opticalscanner having the surface-emitting laser device or the surface-emittinglaser array, and an image forming apparatus having the optical scanner.

BACKGROUND ART

A vertical cavity surface-emitting laser (VCSEL) device is asemiconductor laser device that emits light in a direction perpendicularto a substrate and has received attention due to its (1) competitiveprice, (2) low power consumption, (3) small size and high performance,and (4) ease of two-dimensional integration when compared with anend-surface-emitting semiconductor laser device that emits light in adirection parallel to the substrate.

The surface-emitting laser device has a constriction structure so as toimprove a current inflow efficiency. As the constriction structure, aconstriction structure (hereinafter also referred also to as an“oxidized constriction structure” for convenience sake) obtained byselectively oxidizing an Al (aluminum) As (arsenic) layer is generallyused. The oxidized constriction structure is manufactured in thefollowing manner. That is, a predetermined size of mesas having aselective oxidized layer made of p-AlAs exposed at their side surfacesare formed and then placed in a high-temperature steam atmosphere toselectively oxidize Al from the side surfaces of the mesas. With theoxidation of the Al, non-oxidized regions are formed in the selectiveoxidized layer near the centers of the mesas. The non-oxidized regionsare regions (current injection regions) through which the drivingcurrent of the surface-emitting device passes. Thus, currentconstriction is easily made possible. The refractive index of the layerwhere Al is oxidized (Al_(x)O_(y)) in the oxidized constrictionstructure is about 1.6, which is smaller than that of a semiconductorlayer. Accordingly, since a difference in the refractive index in atraverse direction occurs in a resonator structure and light is trappedat the centers of the mesas, a light-emitting efficiency can beimproved. As a result, excellent characteristics such as a low thresholdcurrent and a high efficiency can be realized.

Meanwhile, since the surface-emitting laser device is susceptible tohumidity (water), various countermeasures have been taken (see, forexample, Patent Documents 1 through 3).

Furthermore, the surface-emitting laser device can suppress the rise ina junction temperature (active-layer temperature), reduce a gain drop,and obtain a high output by immediately discharging the heat generatedin an active layer (see, for example, Patent Document 4).

With the countermeasures disclosed in Patent Documents 1 however,demanded reliability may not be obtained.

Disclosure of Invention

According to a first aspect of the present invention, there provided amanufacturing method for manufacturing a surface-emitting laser devicethat emits laser light in a direction perpendicular to a substrate. Themanufacturing method includes a step of forming a laminated body inwhich a lower reflecting mirror, a resonator structure including anactive layer, and an upper reflecting layer having a selective oxidizedlayer are laminated on the substrate; a step of etching the laminatedbody to form a mesa structure having the selective oxidized layerexposed at side surfaces thereof; a step of selectively oxidizing theselective oxidized layer from the side surfaces of the mesa structure toform a constriction structure in which a current passing region issurrounded by an oxide; a step of forming a separating groove at aposition away from the mesa structure; a step of passivating anoutermost front surface of at least a part of the laminated body exposedwhen the separating groove is formed; and a step of coating a passivatedpart with a dielectric body.

According to a second aspect of the present invention, there is provideda surface-emitting laser device that includes a laminated body in whicha lower reflecting mirror, a resonator structure including an activelayer, and an upper reflecting mirror having a selective oxidized layerare laminated on a substrate; a light-emitting part composed of a mesastructure formed by grooves for constituting a constriction structure inwhich a current passing region is surrounded by an oxide obtained byselectively oxidizing side surfaces of the selective oxidized layer; anda separating groove formed at a position away from the mesa structure.An outermost front surface of a side surface of at least a part of thelaminated body exposed when the separating groove is formed ispassivated.

According to a third aspect of the present invention, there is provideda surface-emitting laser array into which the surface-emitting laserdevice described above is integrated.

According to a fourth aspect of the present invention, there is provideda first optical scanner that scans a surface to be scanned with light.The first optical scanner includes a light source having thesurface-emitting laser device described above; a deflector that deflectslight from the light source; and a scanning optical system thatcondenses the light deflected by the deflector onto the surface to bescanned.

According to a fifth aspect of the present invention, there is provideda second optical scanner that scans a surface to be scanned with light.The second optical scanner includes a light source having thesurface-emitting laser array described above; a deflector that deflectslight from the light source; and a scanning optical system thatcondenses the light deflected by the deflector onto the surface to bescanned.

According to a sixth aspect of the present invention, there is providedan image forming apparatus that includes at least one image carrier; andat least the one optical scanner described above that scans the at leastone image carrier with light modulated in accordance with imageinformation.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram for explaining the schematic configuration of alaser printer according to an embodiment of the present invention;

FIG. 2 is a schematic diagram showing an optical scanner in FIG. 1;

FIG. 3 is a diagram for explaining a surface-emitting laser arrayincluded in a light source in FIG. 2;

FIG. 4 is a diagram showing a cross section taken along the line A-A inFIG. 3;

FIGS. 5A and 5B are diagrams for explaining an inclined substrate;

FIG. 6 is a diagram for explaining a lower semiconductor DBR;

FIGS. 7A through 7C are diagrams (I) for explaining a method formanufacturing the surface-emitting laser array;

FIG. 8 is a diagram (II) for explaining the method for manufacturing thesurface-emitting laser array;

FIG. 9 is a diagram (III) for explaining the method for manufacturingthe surface-emitting laser array;

FIGS. 10A through 10D are diagrams (IV) for explaining the method formanufacturing the surface-emitting laser array;

FIGS. 11A through 110 are diagrams (V) for explaining the method formanufacturing the surface-emitting laser array;

FIG. 12 is a diagram for explaining a positional relationship betweenthe end surfaces of mesas of an upper reflecting mirror, where damagelayers are removed, and the passivated end surfaces of a heat radiatinglayer of a lower reflecting surface;

FIG. 13 shows a transmission electron microscope image (TEM image) takennear the outermost front surfaces of the side surfaces of the heatradiating layer of a lower semiconductor DBR in the surface-emittinglaser array that employs passivation processing in step (11-1);

FIGS. 14A and 14B show a part where an elemental analysis is carried outby Energy-Dispersive X-ray Spectroscopy (EDS) and results of theelemental analysis by the EDS, respectively;

FIG. 15 shows a transmission electron microscope image (TEM image) takennear the outermost front surfaces of the side surfaces of the heatradiating layer of the lower semiconductor DBR in the surface-emittinglaser array that employs the passivation processing in step (11-2);

FIG. 16 is a diagram showing results obtained by carrying out theelemental analysis by the EDS with respect to the heat radiating layer,an As poor layer, and an As rich layer;

FIG. 17 shows a scanning electron microscope image (SEM image) taken ata part where the heat radiating layer is separated;

FIGS. 18A through 18D are diagrams (I) for explaining a modification ofthe method for manufacturing the surface-emitting laser array;

FIGS. 19A through 19C are diagrams (II) for explaining a modification ofthe method for manufacturing the surface-emitting laser array;

FIGS. 20A through 20C are diagrams (III) for explaining a modificationof the method for manufacturing the surface-emitting laser array; and

FIG. 21 is a diagram for explaining the schematic configuration of acolor printer.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, an embodiment of the present invention is described below withreference to FIGS. 1 through 12. FIG. 1 shows the schematicconfiguration of a laser printer 1000 serving as an image formingapparatus according to the embodiment.

The laser printer 1000 has an optical scanner 1010, a photosensitivedrum 1030, an electrifying charger 1031, a developing roller 1032, atransfer charger 1033, a charge removing unit 1034, a cleaning unit1035, a toner cartridge 1036, a sheet feeding roller 1037, a sheetfeeding tray 1038, a pair of resist rollers 1039, a fixing roller 1041,a sheet discharging roller 1042, a sheet catching tray 1043, acommunication control unit 1050, a printer control unit 1060 thatcollectively controls the above units, and the like. Note that theseunits are accommodated at predetermined positions in a printer housing1044.

The communication control unit 1050 controls interactive communicationswith a higher-level apparatus (for example, a personal computer) via anetwork or the like.

The photosensitive drum 1030 is a cylindrical member having aphotosensitive layer at its front surface. In other words, the frontsurface of the photosensitive drum 1030 is a surface to be scanned. Thephotosensitive drum 1030 rotates in the direction as indicated by anarrow in FIG. 1.

The electrifying charger 1031, the developing roller 1032, the transfercharger 1033, the charge removing unit 1034, and the cleaning unit 1035are arranged near the front surface of the photosensitive drum 1030 andarranged in this order along the rotating direction of thephotosensitive drum 1030.

The electrifying charger 1031 uniformly charges the front surface of thephotosensitive drum 1030.

The optical scanner 1010 scans the front surface of the photosensitivedrum 1030 charged by the electrifying charger 1031 with a light fluxmodulated in accordance with image information from the higher-levelapparatus and forms a latent image corresponding to the imageinformation on the front surface of the photosensitive drum 1030. Theformed latent image moves in the direction of the developing roller 1032along with the rotation of the photosensitive drum 1030. Note that theconfiguration of the optical scanner 1010 is described below.

The toner cartridge 1036 stores toner, which is supplied to thedeveloping roller 1032.

The developing roller 1032 attaches the toner supplied from the tonercartridge 1036 to the latent image formed on the front surface of thephotosensitive drum 1030 to form the image information. The latent imageattached with the toner (hereinafter referred also to be as a “tonerimage” for convenience sake) moves in the direction of the transfercharger 1033 along with the rotation of the photosensitive drum 1030.

The sheet feeding tray 1038 stores recording sheets 1040. The sheetfeeding roller 1037 is arranged near the sheet feeding tray 1038. Thesheet feeding roller 1037 picks up the recording sheets 1040 one by onefrom the sheet feeding tray 1038 and conveys them to the pair of resistrollers 1039. The pair of resist rollers 1039 temporarily hold therecording sheet 1040 picked up by the sheet feeding roller 1037 whilefeeding the recording sheet 1040 to a gap between the photosensitivedrum 1030 and the transfer charger 1033 along with the rotation of thephotosensitive drum 1030.

In order to electrically attract the toner on the front surface of thephotosensitive drum 1030 to the recording sheet 1040, a voltage having apolarity opposite to that of the toner is applied to the transfercharger 1033. With this voltage, the toner image on the front surface ofthe photosensitive drum 1030 is transferred to the recording sheet 1040.The recording sheet 1040 on which the toner image is transferred is fedto the fixing roller 1041.

The fixing roller 1041 applies heat and pressure to the recording sheet1040 to fix the toner onto the recording sheet 1040. The recording sheet1040 onto which the toner is fixed is fed to the sheet catching tray1043 through the sheet discharging roller 1042 and stacked on the sheetcatching tray 1043.

The charge removing unit 1034 removes the charge on the front surface ofthe photosensitive drum 1030.

The cleaning unit 1035 eliminates the toner (remaining toner) remainingon the front surface of the photosensitive drum 1030. The front surfaceof the photosensitive drum 1030, from which the remaining toner iseliminated, returns to the position opposing the electrifying charger1031 again.

Next, the configuration of the optical scanner 1010 is described.

As shown in FIG. 2 as an example, the optical scanner 1010 has adeflector-side scanning lens 11 a, an image-surface-side scanning lens11 b, a polygon mirror 13, a light source 14, a coupling lens 15, anapertured plate 16, a cylindrical lens 17, a reflecting mirror 18, ascanning control unit (not shown), and the like. These components areassembled at predetermined positions in an optical housing 30.

Note that in the following description, a direction corresponding to amain scanning direction is briefly described as a “main-scanningcorresponding direction,” and a direction corresponding to asub-scanning direction is briefly described as a “sub-scanningcorresponding direction” for convenience sake.

The coupling lens 15 converts a light flux output from the light source14 into substantially parallel light.

The apertured plate 16 has an apertured part, which defines the beamdiameter of the light flux through the coupling lens 15.

The cylindrical lens 17 forms the image of the light flux, which haspassed through the apertured part of the apertured plate 16, near thedeflecting and reflecting surface of the polygon mirror 13 through thereflecting mirror 18 in the sub-scanning corresponding direction.

An optical system arranged on a light path between the light source 14and the polygon mirror 13 is called a pre-deflector optical system. Inthis embodiment, the pre-deflector optical system is composed of thecoupling lens 15, the apertured plate 16, the cylindrical lens 17, andthe reflecting mirror 18.

The polygon mirror 13 has as en example a six-surface mirror in whichthe radius of an inscribed circle is 18 mm, and each mirror serves asthe deflecting and reflecting surface. The polygon mirror 13 deflectsthe light flux from the reflecting mirror 18 while rotating about ashaft parallel to the sub-scanning corresponding direction at equalspeed.

The deflector-side scanning lens 11 a is arranged on the light path ofthe light flux deflected by the polygon mirror 13.

The image-surface-side scanning lens 11 b is arranged on the light pathof the light flux through the deflector-side scanning lens 11 a. Thelight flux through the image-surface-side scanning lens 11 b is appliedto the front surface of the photosensitive drum 1030 to form a lightspot. The light spot moves in the longitudinal direction of thephotosensitive drum 1030 along with the rotation of the polygon mirror13. In other words, the light spot scans the photosensitive drum 1030.The movement direction of the light spot at this time is the “mainscanning direction.” Furthermore, the rotating direction of thephotosensitive drum 1030 is the “sub-scanning direction.”

An optical system arranged on the light path between the polygon mirror13 and the photosensitive drum 1030 is called a scanning optical system.In this embodiment, the scanning optical system is composed of thedeflector-side scanning lens 11 a and the image-surface-side scanninglens 11 b. Note that at least one turning-back mirror may be arranged onat least one of the light path between the deflector-side scanning lens11 a and the image-surface-side scanning lens 11 b and the light pathbetween the image-surface-side scanning lens 11 b and the photosensitivedrum 1030.

As shown in FIG. 3 as an example, the light source 14 has asurface-emitting laser array 100. In the surface-emitting laser array100, 21 light-emitting parts are two-dimensionally arranged and formedon a substrate and emit laser light in a direction perpendicular to thesubstrate. In other words, vertical cavity surface-emitting laserdevices are integrated into the surface-emitting laser array 100. Thesurface-emitting laser array 100 is a surface-emitting laser arrayhaving an oscillation wavelength of 780 nm. Note that in FIG. 3, thedirection as indicated by M is the main-scanning correspondingdirection, and the direction as indicated by S is the sub-scanningcorresponding direction. Furthermore, in FIG. 3, wirings and electrodepads are omitted for convenience sake.

The 21 light-emitting parts of the surface-emitting laser array 21 arearranged such that an interval between the neighboring light-emittingparts becomes an equal interval c when all the light-emitting parts areorthogonally projected onto an imaginary line extending in the directionas indicated by S. Note that in this specification, the “intervalbetween the light-emitting parts” is a distance between the centers ofthe two light-emitting parts. Accordingly, the front surface of thephotosensitive drum 1030 can be scanned with 21 light fluxes at the sametime.

A cross section taken along the line A-A in FIG. 3 is shown in FIG. 4.Note that in this specification, a laser oscillating direction isdefined as a Z-axis direction, and two directions orthogonal to eachother inside a plane perpendicular to the Z-axis direction are definedas an X-axis direction and a Y-axis direction, respectively.

The surface-emitting laser array 100 has a substrate 101, a lowersemiconductor DBR 103, a lower spacer layer 104, an active layer 105, anupper spacer layer 106, an upper semiconductor DBR 107, and the like.

The substrate 101 has a mirror-polished surface as its front surface. Asshown in FIG. 5A, the substrate 101 is an n-GaAs single-crystalsubstrate in which the normal-line direction of the mirror-polishedsurface is inclined by 15 degrees (θ=15 degrees) toward a crystalorientation [1 1 1] A direction relative to a crystal orientation [1 00] direction. In other words, the substrate 101 is a so-called inclinedsubstrate. Here, as shown in FIG. 5B, the normal-line direction of themirror-polished surface is arranged such that a crystal orientation [0 1−1] direction is defined as a negative X-direction, and a crystalorientation [0 −1 1] direction is defined as a positive X-direction.

As shown in FIG. 6 as an example, the lower semiconductor DBR 103 has afirst lower semiconductor DBR 103 ₁ and a second lower semiconductor DBR103 ₂.

The first lower semiconductor DBR 103 ₁ is laminated on the positiveZ-side of the substrate 101 through a buffer layer (not shown). Thefirst Lower semiconductor DBR 103 ₁ has 37.5 pairs of lowrefractive-index layers 103 a made of n-Al_(0.9)Ga_(0.1)As and highrefractive-index layers 103 b made of n-Al_(0.3)Ga_(0.7)As. In order toreduce electric resistance, a composition inclined layer (not shown)having a thickness of 20 nm, in which compositions are gradually changedfrom one to the other, is provided between the respectiverefractive-index layers. Each of the refractive-index layers is set insuch a manner as to have an optical thickness of λ/4 including ½ of theneighboring composition inclined layer assuming that an oscillatingwavelength is λ. Note that there is a relationship between the opticalthickness and the actual thickness of a Layer as follows. When theoptical thickness is λ/4N, the actual thickness D of the layer isexpressed by D=λ/4 (where N is the refractive index of the medium of thelayer).

The second lower semiconductor DBR 103 ₂ is laminated on the positiveZ-side of the first lower semiconductor DBR 103 ₁ and has 3 pairs of thelow refractive-index layers 103 a and the high refractive-index layers103 b. In order to reduce electric resistance, a composition inclinedlayer (not shown), in which compositions are gradually changed from oneto the other, is provided between the respective refractive-indexlayers. The low refractive-index layers 103 a are set in such a manneras to have an optical thickness of 3λ/4 including ½ of the neighboringcomposition inclined layer. The high refractive-index layers 103 b areset in such a manner as to have an optical thickness of λ/4 including ½of the neighboring composition inclined layer. The second lowersemiconductor PER 103 ₂ is a so-called “heat radiating structure.”Furthermore, the low refractive-index layer 103 a of the second lowersemiconductor DBR 103 ₂ is a so-called “heat radiating layer.”

Referring back to FIG. 4, the lower spacer layer 104 is laminated on thepositive Z-side of the lower semiconductor DBR 103 and made of non-dopedAl_(0.6)Ga_(0.4)As.

The active layer 105 is laminated on the positive Z-side of the lowerspacer layer 104 and has three quantum well layers and four barrierlayers. Each of the quantum well layers is made of Al_(0.12)Ga_(0.88)As,and each of the barrier layers is made of Al_(0.3)Ga_(0.7)As.

The upper spacer layer 106 is laminated on the positive Z-side of theactive layer 105 and made of non-doped Al_(0.6)Ga_(0.4)As.

A part composed of the lower spacer layer 104, the active layer 105, andthe upper spacer layer 106 is called a resonator structure and set insuch a manner as to have an optical thickness of one wavelength. Notethat the active layer 105 is provided at the center of the resonatorstructure, which corresponds to the antinode of a stationary wavedistribution in an electric field, so as to obtain a high stimulatedemission probability.

Furthermore, the heat generated at the active layer 105 is mainlyradiated to the substrate 101 through the lower semiconductor DBR 103.The rear surface of the substrate 101 is attached to a package with aconductive adhesive or the like. The heat is radiated from the substrate101 to the package.

The upper semiconductor DBR 107 is laminated on the positive Z-side ofthe upper spacer layer 106 and has 24 pairs of low refractive-indexlayers made of p-Al_(0.9)Ga_(0.1)As and high refractive-index layersmade of p-Al_(0.3)Ga_(0.7)As. In order to reduce electric resistance, acomposition inclined layer, in which compositions are gradually changedfrom one to the other, is provided between the respectiverefractive-index layers. Each of the refractive-index layers is set insuch a manner as to have an optical thickness of 2/4 including ½ of theneighboring composition inclined layer.

At the position optically λ/4 away from the resonator structure in theupper semiconductor DBR, a selective oxidized layer 108 made of p-AlAsis provided. Note that in FIG. 4, the selective oxidized layer 108 isprovided between the upper semiconductor OCR 107 and the resonatorstructure for convenience sake.

In the following description, one having the plural semiconductor layerslaminated on the substrate 101 as described above is called a “laminatedbody” for convenience sake.

Next, a manufacturing method for manufacturing the surface-emittinglaser array 100 is described.

(1) The laminated body is formed by crystal growth using an organicmetal vapor growing method (MOCVD method) or a molecular beam epitaxialgrowing method (MBE method) (see FIG. 7A).

Here, trimethyl aluminum (TMA) and trimethyl gallium (TMG) are used as agroup III material, and arsin (AsH₃) is used as a group V material.Furthermore, carbon tetrabromide (CBr₄) and dimethyl zinc (DMZn) areused as a p-type dopant material, and hydrogen selenide (H₂Se) is usedas an n-type dopant material.

(2) On the front surface of the laminated body, resist patterns areprovided for forming plural mesa structures (hereinafter brieflydescribed as “mesas” for convenience sake) corresponding to the plurallight-emitting parts. Here, as an example, the square-shaped resistpatterns having a side of 20 μm are provided for parts serving as themesas.

Furthermore, an interval between the neighboring mesas is preferably 5μm or larger so as to electrically and spatially separate the respectivelight-emitting parts from one another. This is because etching controlat the time of manufacturing the surface-emitting laser array becomesdifficult if the interval is too small.

(3) Through the resist patterns as a photomask, the mesas are formed byan ECR etching method using Cl₂ gas. Here, an etched bottom surface ispositioned at the upper surface of the lower spacer layer 104. Note thatif the etched bottom surface reaches the second lower semiconductor DBR103 ₂, the heat radiating layer having a high level of Al compositionsis oxidized in the following oxidation step. In order to avoid this, theetched bottom surface is required to penetrate deeper than the selectiveoxidized layer 108 and stop before reaching the heat radiating layer.Note that if an AlGaInP-system material is used as the lower spacerlayer 104, the control of the etched bottom surface can be improved.Furthermore, the size (length of a side) of the mesas is preferably 10μm or larger. This is because heat may be kept inside during operationsand thus degrades characteristics of the mesas if the interval is toosmall.

(4) The photomask is removed (see FIG. 7B).

(5) The laminated body is heat-treated in vapor. Here, Al of theselective oxidized layer 108 is selectively oxidized from the peripheralparts of the mesas. Then, non-oxidized regions 108 b surrounded byAl-oxidized layer 108 a are caused to remain at the centers of the mesas(see FIG. 7C). Thus, the oxidized constriction structures aremanufactured, which allow the driving current of the light-emitting tobe supplied only at the centers of the mesas.

The non-oxidized regions 108 b are the current passing regions (currentinjection regions). Here, conditions (such as holding temperature andholding time) of the heat treatment are appropriately selected to obtainthe current passing regions 108 in desired sizes based on the results ofvarious preliminary experiments.

At this time, as shown in FIG. 8 as an example, since the lowrefractive-index layers of the upper semiconductor DBR 107 exposed onthe side surface of the mesa contain Al in large amounts, they areoxidized from their exposed parts. The oxidized parts of the oxidizedlow refractive-index layers are several tens of nm in length (depth).The oxidized parts 151 are called damage layers, which give large stressto the mesa and influence the service life of laser light. Note that thelengths of the oxidized parts depend on an Al composition ratio of thelow refractive-index layers of the upper semiconductor DBR 107.

(6) The side surfaces of the mesas are etched by a BHF (bufferedhydrofluoric acid) for about 10 to 15 seconds. Thus, as shown in FIG. 9as an example, the damage layers are removed. In other words,unnecessary oxides on the side surfaces of the mesa forming the oxideconstriction structures are removed. Thus, stress due to oxidation isalleviated.

Meanwhile, the removal of the damage layers must be carried out in anappropriate etching time. The appropriate etching time depends on the Alcomposition ratio of the low refractive-index layers of the uppersemiconductor DBR 107. If an etching time is too much longer than theappropriate etching time, the upper semiconductor DBR 107 may be crackedand broken. For this reason, if the appropriate etching time is notdecided, the step of removing the damage layers may be omitted.

(7) A resist mask for forming grooves for separation (chip-cutting) isprovided on the front surface of the laminated body.

(8) Using the resist mask described above as an etching mask, thegrooves for separation (chip-cutting) are formed by a dry etchingmethod.

(9) The etching mask is removed (see FIG. 10A). Here, the grooves 152reaching the substrate 101 are formed. Thus, the lower semiconductor DBR103 is exposed.

(10) The laminated body is immersed in 5% ammonia water for 40 seconds.

(11) Passivation processing is carried out. Although two methods aredescribed here, the following manufacturing method is the same in eithermethod.

(11-1) The laminated body is placed in a chamber for heat treatment andheld at a temperature of between 350° C. to 400° C. for three minutes ina nitrogen atmosphere. Here, it is conceived that a natural, oxide film,which is generated due to oxygen and water attached to the front surfaceof the laminated body in atmosphere or generated due to a small amountof oxygen and water of the chamber for heat treatment, is converted intoa stable oxide film by heat treatment in a nitrogen atmosphere.

(11-2) The laminated body is placed in a chamber for heat treatment andheld at a temperature of between 350° C. to 400° C. for 25 minutes in anatmosphere concurrently containing oxygen (O₂) and high-temperaturevapor.

In either method, oxidation does not progress from the side surfaces ofthe exposed lower semiconductor DBR 103, and the outermost frontsurfaces of the laminated body are coated with a very thin and stableoxide film 153 (see FIG. 10B).

FIG. 10B is a diagram enlarging one of the parts in which the groovesare formed. The oxide film generated here is much thinner than an oxidefilm generated by a conventional oxidation process and excellent inadhesion to the lower semiconductor DBR 103. Furthermore, it isconceived that the oxide film generated here is a very precise oxidefilm which prevents the penetration of oxygen into the lowersemiconductor DBR 103.

(12) Using a plasma CVD method, a passivation film 111, which is made ofany one of SiN, SiON, and SiO₂ as a dielectric body and has a thicknessof 150 nm through 300 nm, is formed (see FIG. 10C). At this time, asshown in FIG. 10D as an example, the oxide film 153 is also coated withthe passivation film 111. FIG. 10D is a diagram enlarging one of theparts in which the grooves are formed.

(13) The scribe lines of the grooves 152 and the contact holes 154 ofthe upper parts of the mesas are formed (see FIG. 11A). FIG. 12 shows apositional relationship between the end surfaces of the mesas of theupper semiconductor DBR 107, where the damage layers are removed, andthe passivated end surfaces of the heat layer of the lower semiconductorDBR 103.

(14) At regions serving as light-emitting parts on the upper parts ofthe mesas, square-shaped resist patterns having a side of 10 μm areformed, and a p-side electrode material is deposited. A multi-layer filmmade of Cr/AuZn/Au or a multi-layer film made of AuZn/Ti/Au is used asthe p-side electrode material. Here, electrode pads and wiring membersmay be deposited at the same time.

(15) The electrode material of the emitting parts is lifted off to formp-side electrodes 113 (see FIG. 11B). Here, parts other than theelectrodes are masked by a photoresist in advance. Then, after beingdeposited, the electrode material is subjected to ultrasonic cleaning ina solution, such as acetone where the photoresist is dissolved, to formthe electrodes.

(16) After the rear side of the substrate 101 is polished by apredetermined thickness (for example, about 100 μm through 300 μm), ann-side electrode 114 is formed (see FIG. 11C). Here, the n-sideelectrode 114 is a multi-layer film made of AuGe/Ni/Au.

(17) Ohmic conduction between the p-side electrodes 113 and the n-sideelectrode 114 is obtained by annealing. Thus, the mesas are convertedinto the light-emitting parts.

(18) The scribe lines of the grooves 152 are subjected to dicing orscribing to cut out a chip (see FIG. 11D). Thus, the surface-emittinglaser array 100 is completed.

When a high-temperature and high-humidity holding test was conducted inwhich plural surface-emitting laser arrays thus manufactured are leftalone for 1000 hours in a container containing a high-temperature andhigh-humidity atmosphere having a temperature of 85° C. and a humidityof 85%, all the surface-emitting laser arrays were approved. Note thatthe plural surface-emitting laser arrays used in the high-temperatureand high-humidity test include a sample in which the removal of thedamage layers (step (6)) is omitted, a sample employing step (11-1)described above and a sample employing step (11-2) described above asthe passivation processing.

On the other hand, when the same high-temperature and high-humidityholding test was conducted with respect to plural surface-emitting laserarrays manufactured by a conventional manufacturing method, about 6% ofthe plural surface-emitting laser arrays were approved. In other words,reliability can be enhanced by the manufacturing method according to theembodiment of the present invention.

As is apparent from the above, the manufacturing method according to theembodiment of the present invention is carried out as a manufacturingmethod for manufacturing the surface-emitting laser array 100.

In the surface-emitting laser array 100 according to the embodiment ofthe present invention, the lower semiconductor DBR 103, the lower spacerlayer 104, the active layer 105, the upper spacer layer 106, and theupper semiconductor DBR 107 are laminated on the substrate 101. Theoutermost front surfaces of the side surfaces of the lower semiconductorDBR 103 are passivated by the stable oxide film. Furthermore, thepassivated parts are coated with the passivation film 111 made of anyone of SiN, SiON, and SiO₂ as a dielectric body. In this case,reliability can be further enhanced than before.

Meanwhile, a surface-emitting laser is susceptible to humidity (water).Through various experiments or the like, the present inventors havefound that the heat radiating layer which contains a high level of Aland is thicker than other layers is particularly weak in water.

Moreover, according to a conventional manufacturing method, lightetching is carried out for improving adhesion to the passivation filmafter the lower semiconductor DBR is exposed. However, the presentinventors have conducted various experiments or the like and found thefollowing fact. In other words, when the exposed surfaces of the lowersemiconductor DBR are caused to have irregularities by the lightetching, the irregularities may not be sufficiently coated with thepassivation film at parts where the layer is thick even if the filmthickness of the passivation film and film-deposition conditions arechanged. As a result, water penetrates into parts where theirregularities are not sufficiently coated with the passivation film,and the parts are oxidized to cause the breakage of a chip.

According to the embodiment of the present invention, the light etchingis not carried out, but the passivation processing is carried out. Inthis case, since the light etching is not carried out, the exposedsurfaces of the lower semiconductor DBR are not caused to haveirregularities, and the coverage and adhesion properties of thepassivation film are improved even at the heat radiating layer whosethickness is large. Moreover, since the stable oxide film is generatedat the outermost front surfaces of the side surfaces of the lowersemiconductor DBR 103 by the passivation processing, the penetration ofwater into the heat radiating layer can be prevented even if pin holesexist in the passivation film. Thus, resistance to high temperature andhigh humidity is improved, which in turn makes it possible to extend theservice life of the surface-emitting laser array more than before.

Furthermore, according to the embodiment of the present invention, theheat radiating layer constitutes the lower semiconductor DBR, but theprovision of the heat radiating layer is not limited to the lowersemiconductor DBR. For example, even if the heat radiating layer havinga high level of Al is included in the spacer layer or provided in thevicinity of the resonator structure, the step of the passivationprocessing described above can be applied.

Next, the configuration of the lower semiconductor DBR, to which thepassivation processing according to the embodiment of the presentinvention is applied, is described. Here, as an example, an AlAs layerthat also serves as the heat radiating layer and has an opticalthickness of ¾λ is used as the low refractive-index layers of the lowersemiconductor DBR.

FIG. 13 shows a transmission electron microscope image (TEM image) takennear the outermost front surfaces of the side surfaces of the heatradiating layer of a lower semiconductor DBR when step (11-1) wascarried out as the passivation processing. A JEM-2100F manufactured byJEOL Ltd., was used for observing the TEM image. A lower left side inFIG. 13 shows the outermost front surface of the side surface where SiNhaving a film thickness of 150 nm is deposited as the passivation film.An upper right side in FIG. 13 indicates the direction of the inside ofthe semiconductor. The inside of the semiconductor represents the heatradiating layer. A part between the heat radiating layer (AlAs) and thepassivation film (SiN) is a structure manufactured by the passivationprocessing. It is clear from contrast that the structure is a two-layerstructure.

FIG. 14A shows a part where an elemental analysis was carried out byEnergy-Dispersive X-ray Spectroscopy (EDS), and FIG. 14B shows resultsof the elemental analysis. The JEM-2100F manufactured by JEOL Ltd., wasused for the EDS.

The outermost front surface of the lower semiconductor DBR next to thepassivation film is a layer mainly made of the aluminum oxide. Anoxidation distance of the layer mainly made of the aluminum oxide fromthe outermost front surface of the side surface (the thickness of thelayer mainly made of the aluminum oxide) was in the range of 400 nmthrough 450 nm.

A layer next to the heat radiating layer at a position beneath the layermainly made of the aluminum oxide of the lower semiconductor DBR is amixed layer of the arsine oxide and the aluminum oxide. A distancebetween the layer mainly made of the aluminum oxide and the heatradiating layer (the thickness of the mixed layer of the arsine layerand the aluminum oxide) was in the range of 20 nm through 60 nm.

Many of the structures manufactured by the passivation processing arethe layers mainly made of the aluminum oxide, and arsenic was hardlycontained in the layers mainly made of the aluminum oxide.

The mixed layer of the arsine oxide and the aluminum oxide was formed ata position beneath the layer mainly made of the aluminum oxide in thesemiconductor in such a manner as to serve as a cover.

FIG. 15 shows a transmission electron microscope image (TEM image) takennear the outermost front surfaces of the side surfaces of the heatradiating layer of the lower semiconductor DBR when step (11-2)described above was carried out as the passivation processing. However,no passivation film is deposited in a sample observed in FIG. 15.

A lower left side in FIG. 15 shows the outermost front surface of theside surface where tungsten (W) is deposited as a protection film havinga thickness of 100 nm. An upper right side in FIG. 15 indicates thedirection of the inside of the semiconductor. The inside of thesemiconductor represents the heat radiating layer. A part between theheat radiating layer (AlAs) and the protection film (W) is a structuremanufactured by the passivation processing. It is clear from contrastthat the structure is a two-layer structure. The two-layer structureincludes one layer on the side of the protection film, which has lowcontrast and is observed in a porous state, and another layer on theside of the inside of the semiconductor, which has high contrast and isarranged in a narrow range. The thickness of the structure (theoxidation distance from the outermost front surface of the side surface)manufactured by the passivation processing is in the range of 150 nmthrough 250 nm.

FIG. 16 shows results obtained by carrying out the elemental analysis bythe EDS described above. Three parts of the heat radiating layer (AlAslayer), an As poor layer, and an As rich layer in FIG. 15 were measured.

The outermost front surface of the side surface of the lowersemiconductor DBR next to the protection film is an oxide layer (As poorlayer) containing aluminum (Al) and arsenic (As The layer next to theheat radiating layer at a position beneath the outermost front surfaceof the lower semiconductor DBR is also an oxide layer (As rich layer)containing aluminum and arsenic, but its content of arsenic is largerthan that of the oxide layer (As poor layer).

In step (11-2) described above, a layer, which does not contain arsenicand is mainly made of an aluminum oxide, is not formed. A structuremainly made of the aluminum oxide is less precise and has reducedability to sufficiently prevent the penetration of water compared to astructure containing arsenic and aluminum.

Furthermore, when the passivation processing is carried out to form anoxide, a volume change occurs accordingly. The volume change may causedeformation and vulnerability, which in turn breaks the passivation filmeven with a slight impact and degrades moisture resistance. Therefore,the oxide generated by the passivation processing is preferably as smallas possible.

The structure formed in step (11-2) described above does not have thelayer that does not contain arsenic and is mainly made of an aluminumoxide, but it has the oxide layer containing arsenic and aluminum.Therefore, even if the thickness of the layer of the passivated part isthin, the penetration of water can be prevented. Moreover, an oxidelayer containing more arsenic has a greater ability to prevent thepenetration of water.

When a high-temperature and high-humidity holding test was conducted inwhich a surface-emitting laser device manufactured by a conventionalmethod is left alone for 1000 hours in a container containing ahigh-temperature and high-humidity atmosphere having a temperature of85° C. and a humidity of 85%, water penetrated from the side surface ofthe heat radiating layer to cause separation in the heat radiatinglayer. FIG. 17 shows a scanning electron microscope image (SEM image)taken at a part where the heat radiating layer is separated. The heatradiating layer inside the semiconductor is not oxidized, but the heatradiating layer contacting the separated part has high contrast. It isexpected that the part of high contrast of the heat radiating layer isoxidized. In the oxide of the heat radiating layer formed under theatmosphere having a temperature of 85° C. and a humidity of 85%, thepenetration of water cannot be prevented because oxidation progresses.

According to the embodiment of the present invention, the more stableoxide film than the oxide formed under the atmosphere having atemperature of 85° C. and a humidity of 85% is formed on the frontsurfaces of the side surfaces of the lower semiconductor DBR with theapplication of any one of step (11-1) and step (11-2) described above.Therefore, the surface-emitting laser device having high reliability canbe provided.

In the optical scanner 1010 according to the embodiment of the presentinvention, the light source 14 has the surface-emitting laser array 100.Therefore, optical scanning can be carried out in a stabilized manner.

Furthermore, in the surface-emitting laser array 100, the intervalbetween the neighboring light-emitting parts becomes the equal intervalc when all the light-emitting parts are orthogonally projected onto animaginary line extending in the sub-scanning corresponding direction.Therefore, with the adjustment of the timing of lighting of thelight-emitting parts, it can be recognized as a configuration in whichthe light-emitting parts are arranged at equal interval in thesub-scanning direction on the photosensitive drum 1030.

For example, if the interval c in the surface-emitting laser array 100is 10 μm and the magnification of an optical system is 1, 2400 dpi (dotper inch) can be realized. Of course, if the number of thelight-emitting parts in the main-scanning corresponding direction isincreased, or if the surface-emitting laser arrays are arranged suchthat the interval d is narrowed to further narrow the interval c, or ifthe magnification of the optical system is reduced, more high densityand more high-quality printing can be made possible. Note that a writinginterval in the main scanning direction can be easily controlled by theadjustment of timing of lighting of the light-emitting parts.

In this case, the laser printer 1000 can perform printing without losingits printing speed even if writing dot density is increased. Moreover,the laser printer 1000 can further increase its printing speed if thewriting dot density remains the same.

Since the laser printer 1000 according to the embodiment of the presentinvention is provided with the optical scanner 1010, the formation f ahigh-quality image is made possible.

Furthermore, since the service life of the surface-emitting laser deviceis remarkably increased, the reuse of a writing unit or a light sourceunit is made possible.

Note that in the embodiment described above, the heat radiatingstructure has the three pairs of the low refractive-index layers 103 aand the high refractive-index layers 103 b. However, the number of thepairs of the low refractive-index layers 103 a and the highrefractive-index layers 103 b is not limited to three.

Furthermore, in the embodiment described above, each of the heatradiating layers has an optical thickness of 3λ/4. However, the opticalthickness of each of the heat radiating layers is not limited to 3λ/4.In other words, each of the heat radiating layers is only required tohave an optical thickness of λ/4 or larger.

Furthermore, in the embodiment described above, the heat radiating layeris arranged in the lower semiconductor DBR. However, the position wherethe heat radiating layer is arranged is not limited to the lowersemiconductor DBR. For example, the heat radiating layer may be arrangedin the resonator structure or arranged next to the resonator structure.

Furthermore, in the embodiment described above, the heat radiating layeris made of Al_(0.9)Ga_(0.1)As. However, the material of the heatradiating layer is not limited to Al_(0.9)Ga_(0.1)As. The heat radiatinglayer is only required to be made of a material having high heatconductivity. For example, an Al(Ga)As system having an Al compositionof 0.9 or more is preferable, and AlAs having the highest heatconductivity is the most preferable.

Furthermore, in the embodiment described above, the heat radiating layercontaining Al is passivated as the passivation processing. However, anobject to be passivated is not limited to the one applied to the heatradiating layer containing Al. That is, even other layers containing Alcan prevent corrosion when they are passivated. For example, since asemiconductor DBR using AlGaAs having an optical thickness of λ/4 may becorroded when its side surfaces are exposed to the atmosphere, it hasthe advantage of preventing corrosion with the passivation similarly tothe embodiment described above.

Meanwhile, the plural surface-emitting laser devices are generallyformed on a semiconductor wafer at the same time and then divided intoindividual chips. When etching at the time of forming the mesas is notapplied up to the substrate, the side surfaces of the laminated body, onwhich the semiconductor layer constituting the surface-emitting laserdevices is laminated, necessarily emerge at the end parts of the chip.The emerging side surfaces are protected by the passivation processing.

Furthermore, in step (11-1) described above according to the embodimentof the present invention, after being placed in the chamber for heattreatment, the laminated body may be instantaneously added withlow-temperature (200° C. or lower) vapor to have a natural oxide film onits front surface and be held at temperature of 380° C. through 900° C.in a nitrogen atmosphere.

Furthermore, in the embodiment described above, the active layer 105 maybe an active layer composed of three quantum well layers made of GaInPAsas a composition inducing a compression distortion and having a bandgapwavelength of about 780 nm and composed of four barrier layers matchedto the quantum well layers and made of Ga_(0.6)In_(0.4)P as acomposition inducing a tensile distortion. Here, a wide bandgap,(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P, may be used as each of the spacerlayers. In this case, a difference in the bandgap between the spacerlayers and the quantum well layers can be made extremely large comparedwith a case in which the spacer layers are made of an AlGaAs system.Moreover, by containing In, the spacer layers can improve the control ofthe etched bottom surface at the time of forming the mesas. In thiscase, trimethyl indiu (TMI) can be used as a group III material, andphosphine (PH₃) can be used as a group V material.

Furthermore, in the embodiment described above, the mesas at the crosssection orthogonal to a laser oscillation direction are square-shaped,but the shape of the mesas is not limited to a square. For example, theshape of the mesas can be in any shape such as a circle, an ellipse, ora rectangle.

Furthermore, in the embodiment described above, the light-emitting partshave an oscillation wavelength of 780 nm. However, the oscillationwavelength of the light-emitting parts is not limited to 780 nm. Theoscillation wavelength may be changed in accordance with thecharacteristics of the photosensitive body.

Furthermore, the surface-emitting laser array 100 can be applied notonly to the image forming apparatus but also to other purposes. In thiscase, the light-emitting parts may have an oscillation wavelength of 650nm, 850 nm, 980 nm, 1.3 μm, 1.5 μm, or the like in accordance withintended purposes.

Furthermore, in the embodiment described above, the surface-emittinglaser array 100 has the 21 light-emitting parts. However, the number ofthe light-emitting parts is not limited to 21.

Furthermore, in the embodiment described above, instead of thesurface-emitting laser array 100, the light source 14 may bemanufactured by the same manufacturing method as the surface-emittinglaser array 100 so that the light-emitting parts have onesurface-emitting laser device.

Furthermore, in the embodiment described above, as shown in FIG. 18A asan example, regions serving as grooves for separation may be etched atthe same time when the mesas are formed. FIG. 18B is a diagramcorresponding to FIG. 7C; FIG. 18C is a diagram corresponding to FIG.10A; and FIG. 18D is a diagram corresponding to FIG. 10B. FIG. 19A is adiagram corresponding to FIG. 10C; FIG. 19B is a diagram correspondingto FIG. 10D; and FIG. 19C is a diagram corresponding to FIG. 11A. FIG.20A is a diagram corresponding to FIG. 11B; FIG. 20B is a diagramcorresponding to FIG. 11C; and FIG. 200 is a diagram corresponding toFIG. 11D.

Furthermore, in the embodiment described above, the laser printer 1000is used as the image forming apparatus. However, the image formingapparatus is not limited to the laser printer 1000.

For example, an image forming apparatus, which directly applies laserlight to a medium (such as a sheet) that develops a color with laserlight, may be used.

Furthermore, an image forming apparatus, which uses a silver halide filmas an image carrier, may be used. In this case, a latent image is formedon the silver halide film by optical scanning. The formed latent imagecan be visualized by processing equivalent to development processing ina general silver halide photography process. Then, the latent image canbe transferred to a printing sheet by processing equivalent to bakingprocessing in the general silver halide photography process. Such animage forming apparatus can be implemented as a light plate-makingapparatus and a light drawing apparatus that draws a CT-scanning imageor the like.

Furthermore, as shown in FIG. 21 as an example, a color printer 2000having plural photosensitive drums may be used.

The color printer 2000 is a tandem-type multicolor printer that forms afull-color image by superimposing four colors (black, cyan, magenta, andyellow) one on another. The color printer 2000 has components for blackconsisting of a photosensitive drum K1, a charging unit K2, a developingunit K4, a cleaning unit K5, and a transfer unit K6; components for cyanconsisting of “a photosensitive drum C1, a charging unit C2, adeveloping unit C4, a cleaning unit C5, and a transfer unit C6;components for magenta consisting of a photosensitive drum M1, acharging unit M2, a developing unit M4, a cleaning unit M5, and atransfer unit M6; components for yellow consisting of a photosensitivedrum Y1, a charging unit Y2, a developing unit Y4, a cleaning unit Y5,and a transfer unit Y6; an optical scanner 2010; a transfer belt 2080; afixing unit 2030; and the like.

Each of the photosensitive drums rotates in the direction as indicatedby an arrow in FIG. 21. At the periphery of each of the photosensitivedrums, the charging unit, the developing unit, the transfer unit, andthe cleaning unit are arranged in a rotating order. Each of the chargingunits uniformly charges the front surface of the correspondingphotosensitive drum. The optical scanner 2010 applies light to thecharged front surface of each of the photosensitive drums to form alatent image on each of the photosensitive drums. Then, a toner image isformed on the front surface of each of the photosensitive drums by thecorresponding developing unit. Moreover, the toner image in each of thecolors is transferred to a recording sheet on the transfer belt 2080 bythe corresponding transfer unit. Finally, an image is fixed to therecording sheet by the fixing unit 2030.

The optical scanner 2010 has a light source including a surface-emittinglaser array similar to the surface-emitting laser array 100 for eachcolor. Therefore, the optical scanner 2010 can obtain the same effectsas those of the optical scanner 1010. Furthermore, with the provision ofthe optical scanner 2010, the color printer 2000 can obtain the sameeffects as those of the laser printer 1000.

Meanwhile, in the color printer 2000, a color shift may occur due to themanufacturing error, the positional error, or the like of thecomponents. Even in this case, since each of the light sources of theoptical scanner 2010 has the surface-emitting laser array, the colorprinter 2000 can reduce the color shift by selecting the light-emittingpart to be lighted.

As described above, the manufacturing method according to the embodimentof the present invention is suitable for manufacturing thesurface-emitting laser device having high reliability. Furthermore, thesurface-emitting laser device and the surface-emitting laser arrayaccording to the embodiment of the present invention are suitable forimproving reliability more than before. Furthermore, the optical scanneraccording to the embodiment of the present invention is suitable forcarrying out optical scanning in a stabilized manner. Furthermore, theimage forming apparatus according to the embodiment of the presentinvention is suitable for forming a high-quality image.

The present application is based on Japanese Priority Applications No.2008-296195 filed on Nov. 20, 2008, No. 2009-098657 filed on Apr. 15,2009, and No. 2009-230090 filed on Oct. 2, 2009, with the Japan PatentOffice, the entire contents of which are hereby incorporated byreference.

The invention claimed is:
 1. A manufacturing method for manufacturing asurface-emitting laser device that emits laser light in a directionperpendicular to a substrate, the manufacturing method comprising: astep of forming a laminated body in which a lower reflecting mirror, aresonator structure including an active layer, and an upper reflectinglayer having a selective oxidized layer are laminated on the substrate;a step of etching the laminated body to form a mesa structure having theselective oxidized layer exposed at side surfaces thereof; a step ofselectively oxidizing the selective oxidized layer from the sidesurfaces of the mesa structure to form a constriction structure in whicha current passing region is surrounded by an oxide; a step of forming aseparating groove at a position away from the mesa structure; a step ofpassivating an outermost front surface of at least a part of thelaminated body exposed when the separating groove is formed; and a stepof coating a passivated part with a dielectric body.
 2. Themanufacturing method according to claim 1, wherein, in the step ofpassivating the outermost front surface of at least the part of thelaminated body, the outermost front surface is oxidized.
 3. Themanufacturing method according to claim 1, wherein the step ofpassivating the outermost front surface of at least the part of thelaminated body includes a heat treatment in an atmosphere concurrentlycontaining at least both water and oxygen (O₂).
 4. The manufacturingmethod according to claim 3, wherein the step of passivating theoutermost front surface of at least the part of the laminated bodyincludes an ammonia-water immersing treatment conducted prior to theheat treatment.
 5. The manufacturing method according to claim 1,wherein the lower reflecting mirror includes a heat radiating layer. 6.The manufacturing method according to claim 5, wherein the lowerreflecting mirror has plural pairs of low refractive-index layers andhigh refractive-index layers, and the heat radiating layer is the lowrefractive-index layer of at least one of the plural pairs and has anoptical thickness of “an oscillation wavelength/4” or larger.
 7. Themanufacturing method according to claim 1, wherein in the step ofcoating the passivated part with the dielectric body, anyone of SiN,SiO₂, and SiON is coated by a plasma CVD.
 8. The manufacturing methodaccording to claim 1, further comprising: a step of removing anunnecessary oxide from the side surfaces of the mesa structure formingthe constriction structure.